Machines and transmissions are equipped with pumps which maintain a continuous flow of lubricant to the bearings. For bearings, of concern usually are sleeves, bushings or shells whose inner diameter is slightly larger than the diameter of the shaft for which the bearing serves. Pressurized lubricant, usually lubricating oil, is pressed into the gap between the shaft and its bearing element. The shaft is "lifted" by this and floats on the film of lubricant (hydrodynamic lubrication). In this way, less friction, lower temperatures and greater rotational velocity of the shaft are achieved than is the case using ball-bearings filled with lubricant.
The shaft can thus move in the axial direction, that is in the direction toward its ends. Limits are placed on this movement by axial bearing elements of the type being discussed here. If the shaft moves from its specified position, this axial movement is stopped by the axial bearing elements.
One always tries to keep motor components, and, as a part of such group, axial bearing elements, as small as possible, in order to maintain motor and transmission costs low. Axial bearing elements with high load carrying capacity and small size are, consequently, a desired goal.
Laboratory experiments have shown that many of the known constructions of axial bearing elements and their lubrication are ineffective for motor applications. They scarcely increase the load carrying capacity of the bearing.
In the case of a known axial bearing element (thrust bearing) for limiting axial movement of the crank shafts of combustion engines, valleys are provided on the face turned toward the sliding partner. These valleys are very deep, with depths of 0.3 to 0.65 mm. Over a range of 180 degrees, three of these valleys are provided, through which the lubricant can run radially out of the axial bearing location.
Because of the great depth of the valleys, the axial bearing elements must be made very thick. This increases the manufacturing costs, not, however, the load carrying capacity.